The average human scalp contains over 100,000 hair follicles and loses 50 to 100 hairs per day as normal hair fallout. In subjects with male pattern alopecia, a bald area will contain about two-thirds to three-fourths the number of hairs compared to a normal scalp area.
Alopecia affects both males and females and may result from genetic factors, auto-immune disorder, chemotherapy, aging, or local or systemic disease. It can also occur in a number of areas of the body, such as the face, trunk, scalp and limbs. Causes of hair loss can be grouped into the following categories:
Male or Female Pattern Baldness
This type of hair loss requires the presence of male or female hormones, e.g. androgens, but the cause is unknown. The extent of hair loss in any male greatly depends on the genes he inherits from his father, mother, or both. Hair loss begins at the temples or at the top of the head. If male pattern hair loss begins in the mid-teens, subsequent hair loss is usually fairly extensive. Male balding goes in waves. Hair loss may begin in the early 20's, then stop, only to start again in a few years. By the age of 20 to 30 years, 30% of men have bald spots. This continues to rise until age 50-60, when 50% of men are completely bald.
The rate of hair loss is affected by advancing age, the tendency to bald early due to inherited genes, and an overabundance of the male hormone dihydrotestosterone (DHT) within the hair follicle. DHT acts on a hormone receptor within the hair follicle, and thereby slows hair production and produces weak, shorter hair. Sometimes DHT production even stops hair growth completely. Although balding men have above average amounts of DHT in their hair follicles, they usually do not have above average circulating testosterone levels.
Female pattern baldness is not as common as male pattern baldness, but is on the rise. It is confined to the hair predominantly at the top of the head and complete baldness is rare in females.
Toxic Alopecia
This type of hair loss is temporary but typically lasts three to four months, and often is caused by an infectious disease. For example, toxic alopecia may occur as a result of hypothyroidism, diabetes, hormonal problems, vitamin deficiencies, hypopituitarism, parasites, poor digestion, early stage of syphilis, vitamin A or retinoid overdoses, or other cytotoxic drugs.
Alopecia Areata
This is a sudden hair loss in demarcated areas. It can affect any hairy area, but most frequently affects the scalp and beard. Hair loss confined to a few areas is often reversed in a few months even without treatment but recurrence is a possibility. Alopecia areata usually occurs in people with no obvious skin disease or systemic disease, but in rare cases lab tests may show anti-microsomial antibodies to thyroglobulin, gastric parietal cells and adrenal cells.
Scarring Alopecia
Scarring alopecia results from inflammation and tissue destruction. It may be due to injuries such as burns, physical trauma, or destruction after xrays. In these cases, little regrowth is expected. Other causes are cutaneous lupus erythematosus, lichen planus, chronic deep bacterial or fungal infections, deep ulcers, sarcoidosis, syphilis, or tuberculosis. Slow growing tumors of the scalp are a rare cause of hair loss.
While none of these conditions is very well understood, each condition is distressing because hair is often considered an important factor in human social communications and interactions.
Numerous approaches have been suggested for treating hair loss. Two of the most commonly used and accepted compounds for preventing hair loss are minoxidil, the active ingredient in Rogaine® and the 5α-reductase inhibitor, finasteride, the active ingredient in Propecia®. However, cosmetic treatment of age-related hair loss in patients with topical solution of minoxidil or finasteride has resulted in only moderate regrowth of hair in less than 40% of such patients. Indeed, less than ten percent of the men who use Rogaine® achieve satisfactory results. Thus, there is a need in the art for more effective methods of and compositions for treating hair loss. Preferably, new methods and compositions will require fewer applications of active ingredients; provide hair regrowth sooner, in more abundance, and thicker, than presently observed with minoxidil or finasteride treatment.